Generally, liquids like high-purity agents for use in semiconductor manufacturing and common chemical agents are poured into liquid containers, such as polyethylene tanks, at the production plant, and the openings used as inlets and outlets formed in these liquid containers are covered with lids before the liquid containers are shipped out. A known method for extracting the liquid contained in such a liquid container is a siphon-tube method in which gas, such as air, is introduced into the container so that the liquid can be forced outward from the container by the pressure of the gas.
In this siphon-tube method, the lid attached to the opening of the liquid container is first removed, and then a siphon tube serving as a liquid channel and a plug having a gas supply channel are attached to the opening. Subsequently, a socket joinable to a tube for extracting the liquid from the liquid container to the outside and to a tube for introducing gas is connected to the plug, thereby forming a liquid channel for extracting liquid and a gas channel introducing gas. A liquid-container connector of this type is disclosed in, for example, Japanese Unexamined Patent Application, Publication No. 2001-192099.
In Japanese Unexamined Patent Application, Publication No. 2001-192099, a connector equipped with a socket 101 and a plug 102 is provided on an upper surface of a container 104, as shown in FIG. 5 (corresponding to FIG. 4 in Japanese Unexamined Patent Application, Publication No. 2001-192099). An inner bag 103 that contains a liquid, such as a chemical solution, is disposed inside the container 104. A siphon tube 118 is disposed inside the inner bag 103. By introducing gas to the region outside the inner bag 103, the liquid can be delivered outward through the lower end of the siphon tube 118.
FIGS. 6A to 6C (corresponding to FIGS. 5A to 5C in Japanese Unexamined Patent Application, Publication No. 2001192099) illustrate a procedure for connecting the socket 101 and the plug 102. First, a terminal end of the plug 102 is inserted into a terminal end of the socket 101, as shown in FIG. 6A. As the plug 102 is inserted further into the socket 101, a bulge 108 presses balls 132 outward in the radial direction, as shown in FIG. 6B. The balls 132 then press a ring 124 upward against a biasing force of a sleeve spring 125 so as to form a gap between the ring 124 and a projection 123. The balls 132 fit themselves into this gap, thereby permitting further insertion of the plug 102. Further insertion of the plug 102, as shown in FIG. 6C, causes the balls 132 to engage with a ball engagement groove 107 and the sleeve spring 125 to bias the ring 124 so as to bring the ring 124 into abutment with the projection 123, thereby completing the insertion process. Since the balls 132 are in engagement with the ball engagement groove 107 of the plug 102 in this state, the balls 132 prevent the socket 101 from being detached even if the socket 101 is pulled upward.
The socket 101 can be pulled out by lifting a sleeve 121 upward, as shown in FIG. 7 (corresponding to FIG. 6 in Japanese Unexamined Patent Application, Publication No. 2001-192099). The projection 123 also moves upward with the lifting of the sleeve 121. This causes a gap to form between the projection 123 and a stopper ring 122 so that the balls 132 become movable into this gap. In consequence, the balls 132 disengage from the ball engagement groove 107 so as to release the locked state between the plug 102 and the socket 101, whereby the socket 101 can be pulled out from the plug 102.
Although the configuration of Japanese Unexamined Patent Application, Publication No. 2001-192099 allows for a smooth connecting process so long as the sleeve 121 is kept at a downward position without being pulled upward, as shown in FIGS. 6A to 6C, the connecting process may sometimes be performed while the sleeve 121 is pulled upward, depending on the user. In that case, the following problems can occur.
When the sleeve 121 is pulled upward, the balls 132 become positioned below the projection 123, as shown in FIG. 7. Since the balls 132 become freely movable without being restrained within ball-receiving holes 131 (see FIG. 8) formed in a socket body 120, the balls 132 tend to move radially inward so as to protrude inward from the ball-receiving holes 131. If the plug 102 is inserted into the socket 101 in this state, the inwardly protruding balls 132 will roll on the outer surface of the plug 102 (i.e., move from a two-dot chain line to a solid line in FIG. 8) so as to move to a relatively higher position of the sleeve 121 until they come into abutment with the projection 123, as shown in FIG. 8. When the balls 132 come into abutment with the projection 123 in this manner, the balls 132 become clamped between the projection 123 and the plug 102, preventing the plug 102 from being inserted any further into the socket 101. Such a clamped phenomenon of the balls is notable especially when the balls 132 move over past the bulge 108, as shown in FIG. 8.